I was thinking that different planets come with randomly generated metals that affect items and economy in the tribal stage (or equivalent) onwards, and have minor effects on the gameplay, and these elements are:

Inorganic:Iron: colours items made with it a light greyCobalt: colours items made with it a deep blueCopper: colours items made with it a nice orangeChromium: colours items made with it a shiny chromeNiobium: colours items made with it a matte purpleUranium: colours items made with it a glowing greenGold: colours items made with it a metallic yellow

Organic has the gimmick of varying according to the planet's species:Wood: varies with earthy colours but keeps a signature grain effectHide: also greatly varies but takes the effect of the creature skinned for such hideEarth: adopts soil colour of planet

So far I am only thinking that this gives minor effects such as aesthetics but it could create an economy based around it and depending on the species you sell it to.

This is already covered with the compound system. Our current list of compounds is pretty fleshed out, but they are not just for aesthetic effect. They do directly affect gameplay in how they are processed and used.